The invention relates in general to a liquid crystal display (LCD) panel, and more particularly to a transflective LCD panel.
One type of conventional transflective liquid crystal display (LCD) has a dual liquid crystal cell gap. The manufacturing processes for an LCD with a dual liquid crystal cell gap are complicated and the process variations can be hard to control. In contrast, another type of conventional transflective LCD having a single cell gap may have process variations that may be more easily controlled as compared to a transflective LCD having a dual liquid crystal cell gap.
In a transflective LCD having a single liquid crystal cell gap, the length of the optical path of the reflective pixel may be twice that of the optical path of the transmissive pixel. If the reflective pixel and the transmissive pixel are to display the same luminance simultaneously, the effective refractivity of the liquid crystal molecule of the reflective pixel is conventionally one half of the effective refractivity of the liquid crystal molecule of the transmissive pixel. Thus, in a transflective LCD having a single liquid crystal cell gap, the transmissive pixel and the reflective pixel are conventionally driven according to two independent voltage-transmittance curves (V-T curves), respectively.
Accordingly, the transmissive pixel and the reflective pixel may have to be individually driven by two transistors to display the same luminance in the same pixel unit in a transflective LCD having a single liquid crystal cell gap. Consequently, the number of data lines or scan lines, the number of data drivers or scan drivers, the pixel voltages output from the data drivers or scan drivers, and the frequency of the scan signal may have to be correspondingly increased. As a result, the area and the complexity of the driving circuit are greatly increased.
FIG. 1A (Prior Art) is a block diagram showing a pixel driving circuit of conventional transflective LCD 100. Referring to FIG. 1A, transflective LCD 100 includes two scan drivers 110 and 120, data driver 130 and several pixel units. Each pixel unit includes a transmissive pixel and a reflective pixel. FIG. 1B (Prior Art) shows a detailed circuit of pixel unit 140 of transflective LCD 100 of FIG. 1A. Referring to FIG. 1B, pixel unit 140 includes a transmissive pixel and a reflective pixel, which are respectively driven by transistors 141 and 142. Transistors 141 and 142 of pixel unit 140 receive scan signals transmitted from scan drivers 110 and 120 via two scan lines, and a pixel voltage transmitted from data driver 130 through one data line. Data driver 130 outputs the respective different pixel voltages to transistors 141 and 142 at different respective times. As mentioned above, each pixel unit in transflective LCD 100 has two transistors for respectively driving the transmissive pixel and the reflective pixel. Each pixel unit needs two scan drivers and two scan lines to provide two scan signals. Consequently, the circuit complexity of the pixel driving circuit is increased.
FIG. 2A (Prior Art) is a block diagram showing a pixel driving circuit of another conventional transflective LCD 200. Referring to FIG. 2A, transflective LCD 200 includes two data drivers 210 and 220, scan driver 230 and several pixel units. Similar to the pixel units of FIG. 1A, each pixel unit in FIG. 2A includes a transmissive pixel and a reflective pixel. FIG. 2B (Prior Art) shows a detailed circuit of pixel unit 240 of transflective LCD 200 of FIG. 2A. Referring to FIG. 2B, pixel unit 240 includes a transmissive pixel and a reflective pixel. The transmissive pixel and the reflective pixel are respectively driven by transistors 241 and 242. Transistors 241 and 242 of pixel unit 240 each receive a scan signal transmitted from scan driver 230 via the same scan line, and pixel voltages transmitted from data drivers 210 and 220 via two respective data lines. As mentioned above, two transistors in each pixel unit of transflective LCD 200 need two data drivers and two data lines to provide two pixel voltages. Consequently, the circuit complexity of the pixel driving circuit is increased.
FIG. 3A (Prior Art) is a block diagram showing a pixel driving circuit of another conventional transflective LCD 300. Referring to FIG. 3A, transflective LCD 300 includes two data drivers 310 and 320, two scan drivers 330 and 340 and several pixel units. Similar to the pixel units of FIG. 1A, each pixel unit of FIG. 3A includes a transmissive pixel and a reflective pixel. FIG. 3B (Prior Art) shows a detailed circuit of a pixel unit 350 of the transflective LCD 300 of FIG. 3A. Referring to FIG. 3B, the pixel unit 350 includes a transmissive pixel and a reflective pixel. The transmissive pixel and the reflective pixel are respectively driven by transistors 351 and 352. Transistors 351 and 352 of the pixel unit 350 receive scan signals transmitted from scan drivers 330 and 340 via two respective scan lines, and pixel voltages transmitted from data drivers 310 and 320 via two respective data lines. As mentioned above, two transistors in each pixel unit of transflective LCD 300 need two data drivers and two data lines to provide two pixel voltages, and two scan drivers and two scan lines to provide two scan signals. Consequently, the circuit complexity of the pixel driving circuit is further increased.
Although a conventional transflective LCD having a single liquid crystal cell gap has process variations that may be more easily controlled as compared to a transflective LCD having a dual liquid crystal cell gap, two pixel voltages may have to be independently and respectively supplied to the transmissive pixel and the reflective pixel in each pixel unit. Consequently, as discussed above, each pixel unit needs two scan drivers and/or two data drivers to provide the scan signals and the pixel voltages, and two scan lines or two data lines to transmit the scan signals and the pixel voltages. Thus, the area and the complexity of the pixel driving circuit in the transflective LCD are greatly increased so that the aperture ratio of the LCD panel is decreased and the manufacturing cost is also greatly increased.